After c section transvaginal ultrasound at 6 week postpartum necessary?

Hello,

I had c section in end of march, and I went for my 6 week appointment today. My OB gyn said they will do transvaginal ultrasound to make sure uterus lining, cervix, uterus and everything is okay and there are no retained remains etc.

Is this a standard procedure to do transvaginal after c section? Does it hurt I am just so stressed about it. I got my first period at 5 week 5 days and I was bleeding horribly, so they ended up calling me on mext appointment. Ob also said my period should slow down in day or two but if not I should call.

Please shed some light about this postpartum 6 week checkup.

Thanks!